This invention relates to electromagnetically operated actuators for a displacement-type engine having a spring-mass valve actuating oscillatory system maintained by electromagnets in at least two final operational positions of the maximum amplitude of vibration, so that at least two discrete operational positions result in which the dwell time in each such position is controlled by selected excitation of the electromagnets.
Such an actuator, of the general aforementioned type, is required to be adjusted with a very high degree of precision, to avoid functional breakdown, due to manufacturing tolerances, heat expansion, wear, etc., which may occur because the actuated control element (e.g., a valve) and the actuating mechanism (e.g., the armature) do not assume their function-performing operational positions at the same time, i.e., the valve being seated on its valve seat at the same time the armature makes contact with the valve closing electromagnet.
In this regard, West German Pat. No. 23 35 150 provides for a clearance within the transmission element between the actuating mechanism and the valve so that, for valve closing, the contact between the armature and the electromagnet occurs at the same time as the seating of the valve. The impact of the armature on the electromagnet is absorbed by disc springs which are compressed toward the end of the particular stroke involved.
In U.S. Ser. No. 278,393, filed June 29, 1981, now U.S. Pat. No. 4,455,543, an elastic connection is made between the valve stem and the armature to effect the necessary compensation in length and, at the same time, the impact between the armature and the electromagnet is subjected to some dampening.
Also, in order to avoid high mechanical stresses on the contact surfaces, as well as to reduce the noise excitation and chatter as relatively moving parts impact against one another, parts have been used, in conjunction with electromagnets, that produce a pneumatic dampening during all or only a portion of the movements through forces involving a change of volume of enclosed gas. However, special additional parts are required which do not form constituent parts of the electromagnet.
Moreover, dampeners have been directly or indirectly connected to the moving parts of an electromagnetically operated actuator to effect dampening within desired ranges of movement. West German Pat. No. 105 5 091 discloses such an arrangement in which an auxiliary damper is provided for the electromagnet. Dampening is effected by a bellows which is fixedly connected to the armature and is compressed, upon impact against stops, toward the end of its movement, so that the enclosed air space is compressed and is caused to be discharged through an opening. Thus, dampening occurs toward the end of the armature movement.
This type of dampening by the use of auxiliary elements, however, requires a more complex construction for the dampers, for the parts which transmit movement to the armature, and to assure contact engagement between the intended relatively movable elements.